1. Field of the Invention
The present invention generally relates to an optical deflection device for deflecting a light beam, such as a laser beam, which is used, for example, as an element of an optical system for recording digital data on and reading the recorded digital data from an optical disk or optical-magnetic disk, and, in particular, to such an optical deflection device having an electromagnetic driver assembled therein for rotationally driving an optical deflection element, which deflects a light beam made incident thereon.
2. Description of the Related Art
As a representative optical deflection device, a galvano-mirror device is well known. The galvano-mirror device comprises a yoke member, a movable member rotatably supported by the yoke member through the intermediary of a pair of resilient elements, an optical deflection element, such as a prism, a mirror or the like, securely attached to the movable member, and an electromagnetic driver for rotationally driving the movable member with respect to the yoke member.
The electromagnetic driver includes a pair of permanent magnets provided on the yoke member, and an electromagnetic coil provided on the movable member and interposed between the permanent magnets. The electromagnetic coil is disposed in a magnetic field, generated by the pair of permanent magnets, and the movable member, carrying the optical deflection element, is rotated in accordance with Fleming's Rule, when the electromagnetic coil is electrically energized.
In general, there is a demand for the optical deflection device to have a constructional compactness and for the movable member, and therefore the optical deflection element, to exhibit a high-speed drive capability. The high-speed drive capability of the optical deflection element depends upon a product of the magnetic flux density (B) of a magnetic field, produced by the permanent magnets, and a wire length (L) of the electromagnetic coil, i.e. B.times.L. An increase in the magnetic flux density (B) results in a bulkiness of the optical deflection device. Accordingly, the wire length (L) of the electromagnetic coil should be increased in order for the high-speed drive capability of the optical deflection element to be improved.
Nevertheless, the longer the wire length (L) of the electromagnetic coil, the larger a resistance and a self-inductance of the electromagnetic coil. Thus, it is difficult to improve the high-speed drive capability of the optical deflection element by merely extending the wire length (L) of the electromagnetic coil.